The Motor Switch Terminal, Model MST, is a 24 Volt, AC two-position motor. This motor is used with Trol-A-Temp and EWC opposed blade dampers, automatic registers and diffusers. The MST replaces the similar Trol-A-Temp model and the EWC MAN model. Can replace part # MSTN.

The MST requires a Single Pole-Double Throw (SPDT) to operate the motor to the open and closed position. Once the motor reaches the Open or Closed position, the motor's internal end switches cuts power to the motor. Therefore the MST only uses power while moving between open and closed. Once the motor is in either the open or closed position it consumes no power. The MST also has 3 auxiliary end switches that can be used to turn on the furnace, fan or cooling when the damper is open, as well as control a secondary slave damper. See the legend below for the function of each terminal.

NOTE : This Trol-A-Temp MST is shipped in the "OPEN" position

Terminal Functions

(1) 24 Volt Power Common -C(2) 24 Volt Power Hot -R(3) End Switch, makes to 2 when damper is 50% open and breaks when 50% closed. Typically used to turn furnace on for Heating Only.(4) Makes with 5 to drive motor OPEN.(5) Common of switch and makes to either 4 or 6 to operate damper.(6) Makes with 5 to drive damper CLOSED.(X) End switch that makes with 2 when damper is closed. Typically used to control slave damper.(Z) End switch that makes with 2 when damper opens. Typically used to control a slave damper.

Direct replacement for Temp-A-Trol motor. Since the old damper units are no longer available, and the motor is the only thing that will fail, this can save you a lot of time an effort in allowing the old units to live forever.

I was worried I would have to replace the entire zone motor and levor (Not sure the right word for it). I got an estimate from a HVAC company and they wanted $400 to replace it. I took a volt meter and found the voltage was fine going to the motor. I then decided to take a gamble and order this motor as a replacement. It took me about 30 mins to install since it was my first time. I followed the directions (In actuality, I just replaced the color coded wires where they were and tested it before I put it back in the duct), but I did verify it opened and closed the vent now. So I pocketed $300.00 and its been working fine for a about a month. I also know where I can buy a replacement if it happens again.

Works well as direct drop in replacement for the honeywell trol-a-temp damper motors. This is the second one I have purchased and both have performed flawless. Will order more if and when I need them, thanks for a great product.

Took close look at old one once it was out and found that the circular 2-sided switch contacts were dirty and causing it to stop in mid-cycle. Cleaned with tissue and it works fine again; so I have a spare for the other 3 zones that are still going strong despite their age.

The Motor Switch Terminal, Model MST, is a 24 Volt, AC two-position motor. This motor is used with Trol-A-Temp and EWC opposed blade dampers, automatic registers and diffusers. The MST replaces the similar Trol-A-Temp model and the EWC MAN model. Can replace part # MSTN.

The MST requires a Single Pole-Double Throw (SPDT) to operate the motor to the open and closed position. Once the motor reaches the Open or Closed position, the motor's internal end switches cuts power to the motor. Therefore the MST only uses power while moving between open and closed. Once the motor is in either the open or closed position it consumes no power. The MST also has 3 auxiliary end switches that can be used to turn on the furnace, fan or cooling when the damper is open, as well as control a secondary slave damper. See the legend below for the function of each terminal.

NOTE : This Trol-A-Temp MST is shipped in the "OPEN" position

Terminal Functions

(1) 24 Volt Power Common -C(2) 24 Volt Power Hot -R(3) End Switch, makes to 2 when damper is 50% open and breaks when 50% closed. Typically used to turn furnace on for Heating Only.(4) Makes with 5 to drive motor OPEN.(5) Common of switch and makes to either 4 or 6 to operate damper.(6) Makes with 5 to drive damper CLOSED.(X) End switch that makes with 2 when damper is closed. Typically used to control slave damper.(Z) End switch that makes with 2 when damper opens. Typically used to control a slave damper.